It has long been felt that the chemical composition of asphaltic cement will determine its quality, which in turn will ultimately influence the performance of bituminous, or in other words, asphaltic, roadways. However, it has not heretofore been known what precisely needs to be done to the chemical composition of asphaltic cement in order to improve its road characteristics.
There are several factors which are responsible for overall performance of an asphaltic roadway. Many of these are beyond the control of those who make roadways. Some of those major factors appear to be the subgrade and base course quality, environment, construction quality, aggregate quality, asphalt quality, age of the road, and the roadway traffic load. Obviously, changes in any one of these factors will alter the dynamic interaction of all, and the life of the road. One of these factors, which is under the control of those making the road, is the chemical composition of the asphalt cement.
It has heretofore been known and theorized extensively that the chemical composition will determine the asphalt's capability to interact properly with the other mentioned non-controllable factors. However, it has not heretofore been known how to precisely manipulate the asphaltic chemical composition in order to desirably improve bituminous pavement performance.
Common physical tests of asphaltic cement which are performed measure ductility, penetration and viscosity. Those measurements will be referred to herein from time to time as a measure of durability and performance.
Asphaltic pavement comprises the largest portion of the roadways in the United States. The life of those roads will vary greatly depending upon the conditions heretofore mentioned. One of the more important is weather conditions. For example, roadways in mild climates are not subjected to the freeze-thaw cycle and thus could reasonably be expected to have longer life. However, even within the same climatic area, it has been observed from time to time that some roads will crack in an "alligator pattern fashion" very shortly after laying; whereas, other roads in the same area will last much longer. Much speculation has in the past centered around the reasons for such observations, without really knowing the "why".
Accordingly, it is a primary objective of the present invention to control the chemical composition of asphalt such that it alters the normal road deterioration characteristics, thus delaying the period of time it takes for a typical asphaltic road to get harder, and more brittle, and crack.
Another primary objective of the present invention is to allow the reclamation of older asphaltic roads by allowing the "mining" of the road. In other words, the older road is torn up, pulverized and then mixed with aggregate and the "tailor-made" asphaltic compositions to provide a rejuvenated mixture which can then be relaid on the highways.
Another objective of the present invention is to provide economical, reduced cost, repaving techniques which rejuvenate and increase the life of asphaltic roads.
A still further objective of the present invention is to provide a rejuvenating composition, method and technique which allows mining of existing roads and use in both cold mix recycling processes and hot mix recycling processes.
Yet another objective of the present invention is to separate asphalt bottoms into three distinct ingredients, asphaltenes, resins, and oils which may be admixed, at will, to provide controlled ductility and penetration characteristics of a repaved or reclaimed road.
The method of accomplishing these objectives, as well as others, will be evident from the detailed description which follows.
It has, of course, been suggested in the past that one might recycle or "mine" existing asphalt roads, see, for example, Compressed Air Magazine, September 1982 at pages 14 through 17, which is incorporated herein by reference. It has also been suggested in the past that asphalt bottoms may be separated further into heavier and lighter fractions, see for example, Garwin, U.S. Pat. No. 4,125,459, issued Nov. 14, 1978. It has not, however, heretofore been known how to take advantage of known separation technology, such as that expressed in the Garwin patent, in order to tailor-make the composition of asphalt to substantially increasing road life.